Warren’s actual vices tended more toward the ideological. Dwight Eisenhower came to regret the liberal activism of his choice for the Supreme Court, calling it the “biggest damned-fool mistake I ever made.” Other presidents must also have been frustrated by their selections on the far side of life tenure — Ronald Reagan’s appointment of Sandra Day O’Connor or George H.W. Bush’s elevation of David Souter come to mind. Now Chief Justice John Roberts unexpectedly joins the list.

There is little evidence that Roberts is entering a midlife ideological crisis. But his health-care ruling did expose a division between two varieties of judicial conservatism — institutionalism and constitutionalism — that can lead to very different outcomes.

Roberts has emerged as the great institutionalist, concerned primarily about the place of the Supreme Court in American political life. In this view, the court maintains its power by exercising it sparingly — deferring whenever possible to the legislative branch. Institutionalism embodies a temperamental conservatism — a commitment to continuity, humility and prudence.

The main constitutionalists on the court are Antonin Scalia and Clarence Thomas, focused on the rigorous application of the words of the founding document. In this view, the meaning of the text is primary, whatever the political consequences of applying it. Constitutionalism is often accompanied by an understandable complaint: If the conservative response following every period of liberal activism is humility and continuity, then the ideological ratchet turns only leftward.

My natural sympathies are with institutionalism as an antidote to judicial arrogance. Donning a black robe does not assume or create a superior knowledge of public policy. Roberts’s desire to defer, particularly on a divisive issue in the middle of a presidential election, is the right tendency, the correct Burkean instinct.

But judges are also not hired as political philosophers, Burkean or otherwise. Their legitimacy comes from a credible application of the law. And the outcome of the health care case came down to one point of law: Roberts’s interpretation of the statute as a constitutional tax rather than an unconstitutional mandate. In his ruling, Roberts admits this view is hardly the most obvious one: “The question is not whether that is the most natural interpretation of the mandate, but only whether it is a ‘fairly possible’ one.”

The problem is that Roberts’s interpretation is not fairly, or even remotely, possible. If the law had been written in the Roberts version — as a regressive federal tax on the uninsured — there is no chance it would have passed Congress. More to the point, the law that Roberts describes would have covered a different number of the uninsured. Academic studies indicate that people respond differently to tax penalties than they do the legal mandates. “When the imperative to buy insurance,” notes Yuval Levin, “is instead presented as a choice between two options, more people will likely choose the cheaper option (which, for almost everyone, will be paying the tax rather than buying the coverage).”

Why did Roberts not account for this policy distinction? The most natural interpretation is that he didn’t know anything about it. Which is precisely the point. Roberts is not a health policy expert. His clever reinterpretation of the health law would actually change its outcome. This is not an alternate reading but an alternate universe.

Even in a short time, Roberts’s decision has not worn well. What initially seemed wise now smacks of mere cleverness — less a judge’s prudence than a lawyer’s trick. To find the health-care law constitutional, Roberts reimagined it. It was outcome-based jurisprudence, even if the intended outcome was institutional harmony. It was an act of judicial arrogance, even in the cause of judicial deference. And it raises deeper concerns. Unmoored from a reasonable interpretation of the law, institutionalism easily becomes the creed of the philosopher-king — hovering above the balance of powers, tinkering benevolently here and there, instead of living within the constraints of the system.

Roberts has been praised for striking a grand political compromise that the political class could not achieve — for cooling tempers, for granting each side a useful measure of victory and defeat. But who died and left Roberts the job of Daniel Webster? It is the specter of Earl Warren that stirs.

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